The present disclosure relates generally to shoulder prostheses, and more particularly to shoulder prostheses configured for use in shoulders having glenoid vault erosion or defects.
A typical shoulder or glenohumeral joint is formed in a human body where the humerus 10 movably contacts the scapula 12 as shown in FIG. 1. The scapula 12 includes a glenoid fossa 14 that forms a socket against which the head of the humerus 10 articulates. At this socket, the scapula 12 includes cartilage 16 that facilitates such articulation. Beneath the cartilage is subchondral bone 18 that forms a wall of a glenoid vault 20 that defines a cavity which contains cancellous bone 22. During the lifetime of a patient, the glenoid fossa 14 may become worn, especially at its posterior portion thereby causing severe shoulder pain and limiting the range of motion of the patient's shoulder joint. To alleviate such pain and increase the patient's range of motion, a shoulder arthroplasty may be performed.
Shoulder arthroplasty often involves surgical replacement of the glenoid fossa with a conventional glenoid prosthesis such as the one disclosed in U.S. Pat. No. 6,911,047, the disclosure of which is herein incorporated by reference. The glenoid prosthesis, when implanted, provides a new laterally-facing concave bearing surface for articulation with a complementary bearing surface of a natural or prosthetic humeral head. Such conventional glenoid prosthesis is typically formed from UHMW polyethylene, and includes bone anchor(s) such as peg(s) or a keel extending from a back side of the device opposite its bearing surface. So configured, the back side of the prosthesis is typically secured against subchondral bone of the glenoid vault while the bone anchor(s) may extend into the cavity of the glenoid vault whereby it may become anchored to cancellous bone located within the glenoid vault.
However, the subchondral bone support surface and underlying cancellous bone located within the glenoid vault may be significantly deteriorated such that support and anchoring of the conventional glenoid prosthesis may be difficult. Inadequate support and anchoring of the glenoid prosthesis may lead to loosening of the glenoid prosthesis whereby accelerated wear and then failure of the prosthesis may occur.
One document that attempts to address this issue is U.S. Pat. No. 7,329,284 (hereinafter “the '284 patent”), the disclosure of which is herein incorporated by reference. In this document, a prosthetic glenoid component is disclosed that includes a stem portion configured to substantially fill the glenoid vault. While this type of device provides significant advantages for patients having substantially complete erosion of the subchondral and cancellous bone within the glenoid vault, some patients have a significant amount of subchondral and cancellous bone remaining even though partial erosion of the subchondral and cancellous bone has occurred. Removal of healthy subchondral and/or cancellous bone stock in these latter types of patients in order to utilize a prosthesis of the type disclosed in the '284 patent may have disadvantages.
What is needed therefore is an improved shoulder prosthesis for use in patients having deterioration of their subchondral support surface and underlying cancellous bone of their glenoid vault. What is further needed is an improved shoulder prosthesis for use in a patients having deterioration of their subchondral support surface and underlying cancellous bone who still have some healthy bone stock remaining in their glenoid vault.